In commercial subsea diving, supply of air to the diver from the surface is the preferred method (as compared to the use of bottled air carried by the diver) since such a supply scheme places less stringent limitations on diver operating time underwater. Surface supplied air requires the diver to be linked to the surface through an umbilical for the supply of the air along with other services.
In commercial surface air diving umbilical lengths of 75 m with depths down to 50 m combined with an underwater operating radius of up to 25 m typically need to be covered. Alternatively, through the use of saturation diving techniques depths down to 300 m can be reached through the use of a diving bell. In this case an umbilical is required to connect the diver to the bell for the supply of air, with a requirement for the diver being able to operate over a radius of up to 75 m from the bell. In addition umbilicals may be required to connect remote operating vehicles (ROV) or their derivatives to a bell or other installations.
Subsea commercial surface-air diving is globally important in the contexts of off-shore, submerged tidal and ocean power generation installations, wind farms, harbor clearance, pipeline inspection, and wreck inspection/salvage. In addition saturation diving techniques are required in connection with the inspection and maintenance of oil platforms, and submerged well heads, at depths where surface air diving cannot reach. One of the dangers faced by divers in these environments is entanglement or fouling of their umbilicals, which can significantly compromise diver safety and security.